Genetics, Populations, Evolution and Ecosystems

Question 1

Define biotic factors.

Answer 1

Living factors.

Question 2

Define abiotic factors.

Answer 2

Non-living factors.

Question 3

State 4 ways in which a biotic factor could be identified.

Answer 3

1. Species that compete for resources.
2. Species that causes disease or are parasites.
3. Species used for food.
4. Species that are predators.

Question 4

Define a niche.

Answer 4

The role of a species within its ecosystem or community - what it eats, where it eats, when it eats. Niches can be biotic or abiotic and niches can be separated by time, location or behaviour.

Question 5

Define interspecific competition.

Answer 5

Competition between different species. The more similar niches, the more competition.

Question 6

Define intraspecific competition.

Answer 6

Competition within a species. Animals often have their own territories to reduce this competition but there is usually competition for a mate.

Question 7

State two ways in which one would estimate a population size through a sample which is representative and when we would use each.

Answer 7

1. Quadrat - if environment is stable.
2. Transect - if the environment is changing.

Question 8

How does a quadrat remove bias?

Answer 8

It is random because you assign co-ordinates to the area then use dice or a computer to randomly generate co-ordinates.

Question 9

What type of sample is a transect and how?

Answer 9

It is a systematic sample because sample needs to be taken regularly along the transect.

Question 10

What is the process of mark-release-recapture?

Answer 10

For mobile species, a trap it used to capture the organism. They are marked and released back into the population. After a time the trapping is repeated and the number of marked and non-marked are recorded.

Question 11

What is the equation used to estimate a population of a species through marl-release-recapture.

Answer 11

N = (number marked in the first catch) X (total number in second catch).
(divided by) number of recaptures in second catch.

Question 12

State seven rules and/or assumptions that need to be followed during marl-release-recapture.

Answer 12

1. Random collection.
2. Large sample size.
3. Ethical treatment.
4. No net births/deaths/immigration/emigration.
5. Mark - not adding selected pressure.
6. Must give time for population to mix before recapture.
7. Modern - tagging, DNA sample (unique to organism).

Question 13

What is primary succession?

Answer 13

The starting point from bare ground of the gradual directional change of community over time?

Question 14

Why does succession occur?

Answer 14

Due to changing biotic and abiotic factors.

Question 15

State the stages in the progression of primary succession.

Answer 15

Stage 1: A pioneer species colonise bare ground area, as they are adapted to survive in very hostile abiotic conditions. As organisms die, they decompose by microorganisms, adding humus, which leads to the formation of soil which is less hostile, so the soil becomes richer in minerals over time.

Stage 2: Due to less hostile abiotic conditions, other species colonise this area and out-compete the pioneer species as they grow faster and better, they are more fertile, making area less hostile. This increases biodiversity as overtime different habitats are made for different species.

Stage 3: After a few hundred years, woodlands form, preventing light from reaching the floor, so species that are adapted to lower light intensities will out-compete the existing species. The climax community is the most stable as it has the most different habitats and greatest variety of food sources.

Question 16

What is secondary succession?

Answer 16

A community is damaged, and soil is left. Plants then colonise.

Question 17

Define speciation.

Answer 17

The formation of a new species.

Question 18

When does speciation occur?

Answer 18

Speciation occurs when a population is split into two diverse and isolated populations each with a different gene pool. Overtime, they will become two different species and too diverse to reproduce fertile offspring.

Question 19

What are the two types of speciation?

Answer 19

1. Allopatric.
2. Sympatric.

Question 20

What is allopatric speciation.

Answer 20

Allopatric speciation is geographical isolation, overtime, reproductive isolation.

Question 21

Describe the process of allopatric speciation.

Answer 21

1. A geographical isolation splits population into two.
2. This prevents interbreeding between the populations and separate gene pools form.
3. Different random mutations occur in each population and different selection pressures act on each population.
4. This causes the allelic frequency to change differently in each population, they become more genetically diverse overtime.
5. Over time, the two populations become two species (cannot interbreed).

Question 22

What is sympatric speciation?

Answer 22

Sympatric speciation occurs when a mutation causes reproductive isolation.

Question 23

Describe the process of sympatric speciation.

Answer 23

1. Random mutation within a population causes a reproductive isolation for a few individuals.
2. This prevents interbreeding between the populations and separate gene pools form.
3. The new population will pass their alleles on to their offspring and the population will rise.
4. The two populations are two species (cannot interbreed).

Question 24

Define locus.

Answer 24

The location of a gene on a chromosome.

Question 25

Define diploid.

Answer 25

A term applied to cells in which the nucleus contains two sets of chromosomes.

Question 26

Define haploid.

Answer 26

Term referring to cells that contain only a single copy of each chromosome.

Question 27

Define allele.

Answer 27

One of a number of alternative forms of a gene.

Question 28

Define recessive allele.

Answer 28

An allele that is only expressed in the phenotype when both alleles are recessive.

Question 29

Define dominant allele.

Answer 29

An allele that is always expressed in the phenotype of an organism.

Question 30

Define codominant.

Answer 30

When both alleles are expressed in the phenotype.

Question 31

Define homozygous.

Answer 31

When the alleles are the same for a particular gene.

Question 32

Define heterozygous.

Answer 32

When the alleles are different for a particular gene.

Question 33

Define carrier.

Answer 33

Individual who is heterozygous, they have a mutated allele that can be passed onto offspring but is not expressed in their phenotype.

Question 34

Define multiple alleles.

Answer 34

More than two alleles for a gene.

Question 35

Define genotype.

Answer 35

The genetic constitution of an organism.

Question 36

Define phenotype.

Answer 36

The appearance of an organism due to its genotype and its interaction with the environment.

Question 37

Define monohybrid cross.

Answer 37

Determining the expected offspring genotypes and phenotypes from ONE gene.

Question 38

Define dihybrid cross.

Answer 38

Determining the expected offspring genotypes and phenotypes from TWO genes.

Question 39

Define autosomal linkage.

Answer 39

(In dihybrid crosses) When both genes are found on the same chromosome.

Question 40

Define sex-linkage.

Answer 40

When a gene’s locus is on a sex chromosome.

Question 41

Define epistasis?

Answer 41

When the expression of a gene affects the expression of another gene (at a different locus).